When I was younger, I knew I didn't know, but was unsure how to proceed. I did what I read and there was no other sources of information other than the big guys at my gym at the time, who freely admitted they were juicing, so I didn't figure what they were doing was going to work for me. I found at that my workout partner was on gear as well, which explained his sudden poundage increases, while changing nothing else about our shared routine.
I only started to learn something about lifting when I came to this site, though I did get a leg-up when I started reading Pavel Tsatsouline's stuff. This took me on to the old time strength athletes such as Louis Cyr, Bernard Mcfadden, Arthur Saxon on up to the modern strength coaches such as Louie Simmons and that nutjob farmer in Nebraska - whatshisname...Steve Justa, along with Doug Hepburn.
And I find I still don't know enough to coach other people. I'm still experimenting on myself and don't "know things," per se.